Not sure what difference that will make Doug,I tend to come at the problem as being a nominal wheel base,so while bits of engine which stick up in the way effect things a little,generally the engine/trans unit is just what makes it go,and very similar trikes can be made from various power units,since they all fit under similar bonnet space,and usually have plenty of places to bolt extra brackets.Though depending on what we want to build some power plants are easier to work with than others.

So I think that comes down to the age old lack of plan thing,ie what we want to build ?

Once that bit is decided, bending up a few tubes to give a chassis of the right length,and seat height is relatively quick and easy.

This may not be the best answer (regarding your picture),I will look at the picture again later.

I am not a super fan, but with a big old rear engine and drive train, I was thinking something similar to a Boom or other german trike. The frame in the pic would be nice with a Kwak GPZ 900 front end which I still have in the shed.

Ok taking that as size, ninety inch wheelbase, with close to twenty four seat height.allow five, maybe six inches ground clearance and we are already getting near to having a cutting list for the tube lengths.

Regardless,so, hopefully the trail bike yokes are to fit a suitable diameter tube,which means they can be turned into some kind of leading links ?

Meanwhile the 'drawing',Ok the stolen Audi bit is vaguely about right,except the one I have here is the longitudinal mount,so it's long, but not as wide.

As a rough, I would be cutting a pair of top rails at forty four inches, bottom fifty one with forty five bend twenty six inches forward,might merit a brace near the bend,'Boom' seat height I think was twenty four,so top rails eighteenish above lower,I think when I looked at this before,because the motor cants over right hand top rail can terminate at cylinder head,(44 minus length of block),while left has to go all the back to the bellhousing.But hey that was just me looking at the thing as round tube for the front section.If you are going to chuck a cheap glass shell over the topthen go with the box section.I need to stop typing, I suspect I need to eat

Certainly besides the stretching of the legal 'loop-hole' it's going to present some challenges for sure.

While looking at the rear of most 'bike based' trikes there is indeed a lot of unused space,typically I figure a little Peugeot would squeeze in there with a bit of work.

The 'work' would definitely involve chopping a few tubes,to get the Audi installed whole lower right hand rear section of frame would have to come out !

Bottom line is that MSVA test is gona cost less than a four hundred quid,so it's cheaper not to buy the goldwing.a couple of twenty foot lengths of clean new ERW tube don't cost that much,and the time spent messing trying to modify would have seen a whole new chassis built.

Getting one through the test is easy enough,Re-read Beano's Feb-March 2015 mag